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hey I'm Melanie King it from the
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absolute recap and today's video is
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going to recap AP biology unit one
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chemistry of
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[Music]
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life this video is not only going to
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help you study for your unit tests but
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your midterm exams final exams and most
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importantly the AP biology exam in May
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before I start click down in the
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description below so you can get your
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free copy of the AP Bio unit 1 ultimate
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review packet this packet includes a
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unit one video study guide with answer
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key practice multiple choice questions
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Skills Practice sheets with video
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explanations podcast and video resource
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links and an frq task for a breakdown if
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you're taking a non-ap biology class
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either in high school or college these
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resources can absolutely help you too
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now you'll get the most out of this unit
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one recap video with active practice and
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participation so I recommend you print
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the accompanying PDF study guide and
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pause the video periodically to complete
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the practice questions and guided notes
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for each section I'm going to go through
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the topics fairly quickly because the
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goal of this video is to help you dust
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off the concept cobwebs so that you can
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start to make connections at the end of
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the video you'll want to check your
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study guide responses using my answer
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key and then go back to rewatch any
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areas that gave you trouble all right
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listen I know it's tempting to cut
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corners but if you skip right to the
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answer key and you never try the
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questions first yourself then you aren't
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utilizing this video and the ultimate
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review packet to its fullest and I want
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you to gain that confidence in biology
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so that you can do your absolute best in
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your class and on assessments so no
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peeking at that answer key until later
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if you're getting confused throughout
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the video on some of the individual
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Concepts and you need more information
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check out the absolute recap biology
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Edition podcast and our YouTube channel
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for help this summary video is going to
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review all of the main unit one topics
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according to the College Board
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curriculum you can use these timestamps
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listed here to Jump Ahead or go back to
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a specific subtopic at any time all
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right let's zoom out I know this is
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biology but we have to start with the
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foundation in chemistry if we don't
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focus on the microscopic first then
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nothing that happens on the macroscopic
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level will make any sense a strong
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understanding on what influences the
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chemical behavior of an atom will help
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you draw connections between molecular
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structure and function and make
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predictions for cellular processes every
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organism needs to obtain energy and
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exchange matter with the environment so
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let's start with an introduction to
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water and review the most common
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elements and reactions for life then
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I'll recap the four groups of biological
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molecules carbohydrates proteins lipids
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and nucleic acids which will make many
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appearances in all eight units of AP Bio
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let's zoom
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in water might be the most amazing
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molecule on Earth and it can defy
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gravity how well I'll tell you but we
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need to sketch it out first good old H2O
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two elements of hydrogen for every
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element of oxygen form with polar calent
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bonds oxygen is more electron negative
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and has more pull on the shared
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electrons with hydrogen consequently
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oxygen has a partial negative charge
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while each hydrogen atom has a partial
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positive charge this uneven distribution
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of Charge results in a polar molecule of
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water that makes life possible if we can
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recall our chemistry background we know
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that opposite charges attract and like
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charges repel because water is polar it
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will attract to and bond with other
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polar or charge molecules even earning
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the title the universal solvent in fact
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almost all of water's unique properties
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are due to its polarity and ability to
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form hydrogen bonds because opposite
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charges attract a hydrogen bond forms
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between a partial positive hydrogen of
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one water molecule and a partial
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negative oxygen of another water
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molecule when we look at water as a
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collective we'll find hydrogen bonds
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forming between adjacent water molecules
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and polar calent bonds forming within
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water molecules hydrogen bonding is the
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foundation by which water molecules
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interact with other things in liquid
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water hydrogen bonds are continuously
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breaking and reforming boiling water has
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to break those hydrogen bonds in order
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to cause the water molecules to move
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more rapidly which is why water has a
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high specific heat however when water
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freezes the hydrogen bonds become more
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stable and the water molecules get
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pushed farther apart in less dense this
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is why ice floats on water the three big
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properties of water you need to know for
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the exam are adhesion cohesion and
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surface tension water is attracted to
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water called cohesion and to other polar
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or charged things called adhesion both
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cohesion and adhesion give water its
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remarkable ability to defy gravity let's
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look at a plant water moves vertically
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from the roots to the leaves through
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adhesion to the walls of plant
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vasculature and cohesion to other water
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molecules as transpiration occurs at the
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leaves there is a barrel of monkey
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action in which water molecules pull up
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on the water molecule below it you might
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have also seen this gravity defying
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stunt in a graduated cylinder during lab
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a meniscus forms the bottom curve of a
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graduated cylinder because the forces of
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adhesion to the glass are stronger than
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cohesion between water molecules water
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literally jumps up the sides water also
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has remarkable surface tension due to
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cohesive and adhesive forces Es as seen
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in a droplet of water or Morning Dew
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that forms on a blade of grass surface
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tension is also why certain insects can
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literally walk on water the interaction
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their body has with the water is weaker
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than the hydrogen bonds between the
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water molecules
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themselves organisms must exchange
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matter with the environment to grow
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reproduce and keep themselves organized
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quick Science Background review matter
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is made up of atoms has mass and takes
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of space for example rocks Tre trees and
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people are made of matter while energy
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is not atoms contain three subatomic
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particles protons are positively charged
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found in the nucleus and are represented
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as the atomic number on the periodic
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table neutrons have no charge and are
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also found in the nucleus electrons have
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a negative charge and are found
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surrounding the nucleus in rings because
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electrons are the most peripheral of the
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three subatomic particles they will be
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involved in bonding with other atoms
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metabolism is the sum of all chemical
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reactions that take place within an
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organism those that are bond breaking or
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catabolic and those that are Bond
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forming or anabolic we have to do both
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to be biologically successful when
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organisms obtain matter they can use the
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raw materials to build useful molecules
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for biological processes for example
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organisms taken glucose as a reactant
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for cellular respiration and carbon
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dioxide for photosynthesis what do you
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think of when you hear the word organic
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images might come to mind of apples
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grown without pesticides or grass-fed
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cows but in science organic molecules
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contain car carbon because carbon has
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four veence or outer ring electrons it
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forms four calent bonds with other
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elements these bonds can be single
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double or triple causing molecular
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shapes of straight chains Branch chains
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and Rings carbon is so versatile the six
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most common elements found in living
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things are carbon hydrogen nitrogen
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oxygen phosphorus and sulfur carbon
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hydrogen and oxygen are represented in
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all biological molecules nitrogen will
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never be found in in carbs and lipids
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but is always a component of nucleic
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acids in their nitrogenous base and
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proteins and the amino group even though
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nitrogen is the most abundant gas in the
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atmosphere it will need to be taken in
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through food or absorbed from the soil
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the final two elements make infrequent
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appearances phosphorus will always be in
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nucleic acids as a component of the
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backbone of DNA and it will appear in
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lipids that are phospholipids the
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presence of a phosphate group gives DNA
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a negative charge and phospholipid heads
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they polarity and subsequent hydrophilic
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Affinity sulfur makes its only
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appearance in some R groups of proteins
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and influences protein folding through
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the formation of disulfide
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bridges water is a key player in two of
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our primary chemical reactions of
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metabolism dehydration reactions are
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used to join monomers together and form
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a larger polymer it's exactly as
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described to dehydrate to take out water
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so if you link two adjacent monomers you
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can pull hydroxy from water end and a
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hydrogen off of the other removing H2O
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the electrons left behind on those
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monomers are now available to Coal bond
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together in contrast hydrolysis
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reactions add water to break a polymer
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into monomers when this occurs we stick
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a hydroxy onto one monomer and a
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hydrogen onto the
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other the remaining three sections of
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unit one cover the four biological macro
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molecules and properties structures and
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functions instead of jumping back and
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forth for each type Within sections 1.4
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1.5 and 1.6 I'm going to review each
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Macro Molecule individually beginning
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with proteins then carbohydrates lipids
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and lastly nucleic
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acids proteins are polymers formed from
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amino acid monomers an amino acid is
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made up of one Central carbon atom that
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forms four single calent bonds one is to
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hydrogen another is to an acidic carboxy
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group and a third is to a basic amino
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group the fourth calent bond is to an R
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Group which is a substitute for
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different side chains that give each of
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the 20 different amino acids their
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unique chemical properties these
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properties could be hydrophobic
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hydrophilic or even ionic when amino
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acids link together dehydration
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synthesis occurs between an amino group
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of one monomer and the carboxy group of
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the other the calent bond formed between
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them is referred to as a peptide bond
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and when you get many peptide bonds in a
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row you formed a poly peptide
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polypeptide chains the primary structure
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of proteins are formed during the
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process of translation at a ribosome in
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UK carots the newly synthesized
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polypeptide is released for further
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processing by the rough endoplasmic
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reticulum and shipping by the Gogi body
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several scientists were initially
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convinced that proteins were the
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molecule of heredity not DNA it made
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sense they have more alphabet in their
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chemistry than its counterpart DNA with
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20 amino acids as compared to four
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nitrogenous bases and you can form a lot
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more diverse structures for a multitude
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of functions with proteins than you can
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with DNA proteins have four levels of
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structure as it bends and folds in upon
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itself one wrong amino acid and the
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protein folding will be incorrect
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potentially causing an error in function
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primary structure is a chain of amino
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acids from the N Terminus to the C
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Terminus secondary can either form an
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alpha helix or a beta pleated sheet
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through local folding from backbone
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hydrogen bonding tertiary structure has
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a specific 3D shape when Alpha helices
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and beta sheets fold further inwards due
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to R Group bonding interactions the
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final level of structure is quinary
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which has two or more separate amino
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acid chains interacting and bonding
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together the specific structure that
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each protein has is dependent upon the
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chemical properties of the R Group and
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can be influenced by environmental
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factors R Group side chains that are
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hydrophilic or charged fold outward
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toward the aquous environment while
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those that are hydrophobic face the
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interior ior of the protein protein
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structure denatures when hydrogen bonds
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are disrupted this shape change directly
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affects the protein's function and can
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sometimes be reversed since primary
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protein structure is not changed
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proteins practically do everything for
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the cell and even this impressive list
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I'll discuss now is incomplete they are
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a key component in cellular membranes
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with roles in transport recognition
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movement and communication integral
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membrane proteins have hydrophobic
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regions that interact with phosph popid
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tails and hydrophilic regions that are
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adjacent to the heads some integral
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proteins have specific molecular
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chemistry internally forming a channel
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these channels may be gated and allow
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specific ions or small molecules to
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cross the membrane through facilitated
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diffusion or active transport peripheral
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proteins like hormones and antigens
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they're more Loosely attached to the
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membrane and are involved in cell
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recognition and communication membrane
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proteins can also provide anchorage for
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the cytoskeleton aing in structural
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support and cellular movement and lastly
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proteins also form enzymes that catalyze
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chemical reactions for specific
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substrates for example the enzyme sucra
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has a specific active site which fits
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the substrate sucrose a disaccharide
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this enzyme facilitates the hydrolysis
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reaction of sucrose into monomers
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glucose and
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fructose carbohydrates only contain the
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elements carbon hydrogen and oxygen in a
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1:2:1 ratio they are polysaccharide
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formed from monosaccharide monomers
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which join to other monosaccharides with
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a specific type of calent bond called a
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glycidic linkage these biological
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molecules can form long chains or ringed
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structures formed by autot tropes and
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disassembled by nearly all living things
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carbohydrates are the primary source of
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chemical energy for the cell and serve
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as structural material monosaccharides
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like glucose and fructose as well as
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disaccharides such as lactose and
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sucrose are often used as fuel sources
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for the cell glucose C6 h126 takes the
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main stage in AP Bio during cellular
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respiration in the mitochondria and
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photosynthesis in the chloroplast larger
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polysaccharides such as cellulose in
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plant cell walls and kiten and animal
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exoskeletons can be used for structural
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support the polysaccharides starch and
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glycogen are used for long-term energy
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storage in plants and animals
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respectively the primary contrast and
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types of polysaccharides is in their
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glycosidic linkage branching patterns
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and functions many carbs look like
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chemical twins at First Sight but
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organisms can tell the difference
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glucose has an identical chemical
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formula to the isomer fructose and
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galactose but its atoms are arranged
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differently starch and cellulose are
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both formed from consecutive glucose
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monomers but have varying linkage at the
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1 14 Bond even these small differences
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are enough for enzyme substrate
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specificity which is why glucose is used
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for cellular respiration not fructose
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and animals can digest starch but not
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cellulose lipids are very diverse group
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of hydrophobic molecules that are
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non-polar due to their hydrocarbon
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chains they contain the elements carbon
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hydrogen and oxygen and sometimes
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phosphorus when forming membranes unlike
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carbohydrates lipids have a ratio of
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hydrogen to oxygen that is much greater
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than 2: 1 instead of an elemental ratio
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of 1: 2: 1 like carbs
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you could say one to two to few
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additionally lipids don't have a true
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monomer as there's no structural pattern
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of repeating units the different lipid
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varieties fats phospholipids and
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steroids all have unique structures for
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specific roles within organisms fats
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contain a glycerol and long hydrocarbon
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fatty acid chains a saturated fatty acid
00:15:21
is named for a literal Elemental
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saturation of hydrogens if all electrons
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within a hydrocarbon chain are occupied
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with single bonds to hydrogen then the
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fatty acid tails are straight and more
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closely packed together if the fatty
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acid chains are unsaturated that means
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there's at least one carbon to carbon
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double bond and a resulting Bend in the
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fatty acid chain in this circumstance
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the Tails cannot be closely packed
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together and are less dense put Three
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fatty acid chains with glycerol and you
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have the fat triglyceride an important
00:15:52
energy source attach long fatty acid
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chains to alcohol and you get waxes
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lipids that play a role in water Reg
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potion of plants and animals perhaps the
00:16:01
most common lipid or common to AP Bio at
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least is the phospholipid phospholipids
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are amphipathic with two hydrophobic
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fatty acid tails and a hydrophilic head
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the hydrophilic head has a glycerol a
00:16:13
modified phosphate group and often a
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Coline group the properties of
00:16:17
phospholipids and their nature of
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forming a bilayer makes them the ideal
00:16:21
molecule to make up all cellular
00:16:23
membranes because the intracellular and
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extracellular environments are aquous
00:16:27
membranes are B layered with Tails
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facing inwards this allows certain cells
00:16:32
and membrane bound organel to
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compartmentalize their functions
00:16:36
additionally different types of
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phospholipids in cell membranes allow
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the organism's flexibility to adapt to
00:16:42
different environmental temperatures
00:16:44
lastly steroids which have four fused
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carbon rings with attached functional
00:16:48
groups they look very different from any
00:16:51
other lipid with hydrocarbon chains but
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they'll still be non-polar and
00:16:54
hydrophobic you can find steroids in
00:16:57
cell membranes like cholesterol
00:16:59
as well as with signaling molecules like
00:17:03
hormones genetic information is
00:17:05
transmitted from one generation to the
00:17:07
next through DNA or RNA both of these
00:17:09
polymers are examples of nucleic acids
00:17:12
which are made of monomers called
00:17:13
nucleotides a nucleotide has three parts
00:17:16
a pentos sugar a phosphate group and a
00:17:19
nitrogenous base all coal bonded
00:17:21
together nucleic acids have a linear
00:17:23
sequence with directionality designated
00:17:26
as five Prime on the phosphate side of
00:17:28
the sugar and three Prime on the hydroxy
00:17:30
side of the sugar it is important to
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recognize that double stranded DNA is
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anti-parallel meaning that one side of
00:17:37
the backbone is oriented 5 Prime to 3
00:17:39
Prime while the Strand across fromit is
00:17:41
3 Prime to 5 Prime directionality will
00:17:44
be very important when discussing
00:17:46
molecular orientation and enzyme binding
00:17:48
during processes such as replication
00:17:51
transcription and translation the
00:17:53
difference between DNA and RNA sugars
00:17:55
occurs at the two prime carbon RNA has
00:17:58
ribos which contains a hydroxy group at
00:18:00
the two prime carbon DNA has deoxy ribos
00:18:04
which is missing the oxygen at the two
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prime carbon a nucleotide phosphate
00:18:08
group is calent bound to the five Prime
00:18:10
carbon of the Pento sugar within a
00:18:12
nucleotide and to the three prime carbon
00:18:15
of the pentos sugar of an adjacent
00:18:17
nucleotide alternating sugars and
00:18:19
phosphates form the backbone of each
00:18:21
nucleic acid through the formation of a
00:18:23
specific type of calent bond called a
00:18:25
phospher bond the phosphate group has a
00:18:27
negative charge which is why DNA samples
00:18:30
migrate towards the cathode side during
00:18:32
gel electropheresis phosphate groups are
00:18:35
the same in RNA and DNA the last part of
00:18:37
a nucleotide is the nitrogenous base
00:18:40
which encodes the genetic information
00:18:42
the nitrogenous base is arranged
00:18:44
perpendicular to the backbone and cently
00:18:46
bonded to the pentos sugar at the one
00:18:48
prime carbon there are five different
00:18:50
types of nitrogenous bases grouped into
00:18:53
two categories the purines are double
00:18:55
ringed nitrogenous bases and include
00:18:57
guanine and Adine these are found in
00:19:00
both DNA and RNA molecules the peridin
00:19:04
are single ring nitrogenous bases and
00:19:06
includes cytosine thyine and uracil
00:19:09
cytosine is common to both nucleic acids
00:19:12
whereas thyine is only in DNA and urasil
00:19:15
is only an RNA adenine will always bond
00:19:18
with thyine or uracil with two hydrogen
00:19:21
bonds and guanine will always bond with
00:19:23
cytosine with three hydrogen bonds to
00:19:27
recap water is an amazing molecule whose
00:19:31
polarity influences hydrogen bonding and
00:19:33
all of its properties like cohesion
00:19:35
adhesion and surface tension water is
00:19:38
formed through dehydration reactions and
00:19:40
added when dividing polymer chains
00:19:42
during hydrolysis reactions organic
00:19:45
molecules are made of carbon and form a
00:19:47
variety of structures through bonding
00:19:48
patterns with the elements hydrogen
00:19:50
nitrogen oxygen phosphorus and sulfur
00:19:53
organisms obtain these elements from
00:19:56
their environment and metabolize
00:19:57
polymers to grow reproduce and maintain
00:20:00
organization the four major biological
00:20:03
molecules are carbohydrates proteins
00:20:05
lipids and nucleic acids carbohydrates
00:20:08
are formed from monosaccharides and
00:20:10
provide energy and structural support
00:20:13
proteins are polypeptides made of amino
00:20:15
acids which fold into specific shapes
00:20:17
through hydrogen bonding in our group
00:20:19
interactions lipids are non-polar
00:20:21
hydrophobic molecules including fats
00:20:24
phospholipids and steroids and nucleic
00:20:26
acids are the molecule of heredity with
00:20:28
directionality formed from nucleotide
00:20:31
monomers pH we made it a full recap of
00:20:34
AP biology unit 1 chemistry of life and
00:20:37
now it's time for you to practice
00:20:38
applying this information if you haven't
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already grabbed your free copy of the AP
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it's the ultimate way for you to do your
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absolute best in your biology class and
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on the AP biology exam in may now if
00:20:57
you've already finished the unit one
00:20:58
study guide for this video then
00:21:00
definitely check your responses with my
00:21:02
answer key to verify your understanding
00:21:04
for all the different concepts you can
00:21:07
access these answers for free in the
00:21:09
ultimate review packet then you'll want
00:21:12
to take the unit one practice multiple
00:21:14
choice questions where you'll get
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instant feedback on your answers and an
00:21:18
explanation for why the answers are
00:21:20
correct and why the other choices
00:21:22
weren't these are also free if you want
00:21:25
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00:21:27
practice for unit 2 through 8 so you can
00:21:30
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00:21:32
sure to purchase the AP biology ultimate
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review packet it has unit specific
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00:21:53
for unit 2 cell structure and function
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